This invention relates to multiple-plate structures of zonal design, such as a double-plate structure, for forming a part which may be a part of a vehicle or a vehicle body, in which the formed part is subjected to a shaping process, for example a deep-drawing, folding or stamping process.
It is conventional practice to design a plate-structure part intended for a part-shaping operation with a thickness which varies in zones according to the mechanical loads to which the zones of the resulting part will be subjected. It is also known to adapt local zones of such a plate-structure part, e.g. for hinge and shock-absorber receptacles, for attachment regions for doors and flaps and for attachment regions for beams or other load-bearing elements, with a thickness which varies in accordance with predeterminable load condition occurring during the use of the formed part in order to avoid unnecessary material input and to achieve a reduction in weight. Such varying thickness plate design also permits a reduction in the initial thickness of such a plate-structure part by using a thinner base plate. Larger plate thicknesses are accompanied by greater plate strength, in particular torsional rigidity, bending strength and also greater compressive and tensile strength.
In conventional tailored blanks, plate strips of different thickness are joined together for this purpose, for example a thinner plate strip may be arranged between thicker plate strips, in order to be subsequently formed together into a shaped part. There are limitations on the use of these tailored blanks with respect to the adaptation of the material thickness to the respective load profile of the formed part used in the vehicle, i.e. the formed part is also still reinforced in zones in which it does not need to be reinforced. There are, therefore, corresponding limits placed on the reduction in weight when using tailored blanks.
A deep-drawn or stamped plate-structure part having a partial double-plate part structure and a manufacturing method for this are described in German Offenlegungsschrift No. 43 07 563. This plate-structure part is formed in multilayers from a base plate and reinforcing plates arranged in zones on the base plate and is manufactured in such a way that the reinforcing plates are fastened at least partly to the base plate before the part is formed and are then undetachably connected to the base plate after the part is formed. The plate-structure part described in this document also is a so-called multiple-plate structure in which a first reinforcing plate is disposed on a base plate and a further reinforcing plate is disposed in a predetermined zone on the first reinforcing plate. The zonal arrangement of a plurality of further reinforcing plates on the first reinforcing plate is also possible.
Such a multiple-plate structure may also be formed as a unit. With a multiple-plate structure, it is now possible to largely adapt the thickness of the plate-structure part to the load profile to be applied to the formed part and to limit the spatial area of the reinforcing plates to a minimum and to reinforce the base plate only exactly where this is absolutely necessary. In principle, it is also possible in this case to combine different materials or different material qualities with one another, for example to use a reinforcing plate having a higher strength than the base plate at zones which are relevant in terms of strength or in the region of force-application points in order to obtain an optimum result not only with respect to the mechanical requirements but also with regard to appearance and cost. However, the method for manufacturing such a multiple-plate structure is complicated and the forming process can be problematic, since at least three plates each, lying one above the other and only partly fastened to one another, have to be shaped together.